In a message dated 98-01-30 05:18:48 EST, you write:

<<
 Tom, thanks for the advise. I bought a 16F84, programmed a few 1's and 2's:
 the result was the same as with the 12c508.
 I got a brand new programmer from my distributer, still the same problem.
 So, the problems are caused by faul communications with the parallel port of
 the 286 computer. A known problem??

 Leo van Loon
  >>
Leo and Tom,
I have had the same problem with my parralax programmer.  My problems started
when I upgraded my unit to version 4.xx of the firmware.  The only way I get
it to reliably function now is to use my ZIP drive as a buffer.  If I plug
directly into the parrallel port of my laptop I get all kinds of errors.  If I
plug my ZIP drive into the laptop and plug the programmer into the ZIP drive
it works fine.

Go figure

Dave Duley